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A Look at Obesity and Its Lesser-Known Causes

Overweight individuals are at a much higher risk for serious health complications including cardiovascular disease, diabetes, musculoskeletal diseases, and even cancer. According to the Centers for Disease Control and Prevention (CDC), the percentage of overweight and obese adults in the United States, aged 20 years and older totaled 69%, between 2011 and 2012. Given such overwhelming statistics on obesity and obesity-linked illnesses, there have been many studies and animal models to uncover the inner workings of fat, or adipose tissues to better understand the obese state.

The most widely considered aspect in impacting weight gain or loss is food intake versus energy expenditure. For example, weight loss can be achieved by taking in less energy (i.e., food) than is being used through physical activity. However, there are many other factors associated with the obese state, including one’s genes and endocrine factors. Animal models have allowed researchers the means to study each of these factors at great length.

For example, in animal studies, alteration in protein expression via manipulation of genes linked to fat regulation has proven to impact weight gain and loss in a predictable and reproducible way. Additionally, endocrine factors such as ghrelin (released from the stomach and part of the small intestine) and leptin (released primarily from white adipose tissue stores), can greatly stimulate or inhibit one’s appetite, respectively.

Adipose tissues (fat depots), primarily known as energy stores in the form of fat, are actually considered an endocrine organ, storing and releasing endocrine factors, and communicating with the hypothalamus through these factors. Within the hypothalamus lie orexigenic (appetite stimulating) and anorexigenic (appetite suppressing) pathways that regulate appetite through the release of orexigenic or anorexigenic peptides. These peptides, and the genes that regulate their expression are being studied to better understand the obese state.

White adipose tissues secrete appetite-suppressing leptin, along with a number of other factors associated with obesity. These factors, also known as adipokines, are incredibly diverse in nature, and include leptin, adiponectin, apelin, chemerin, interleukin-6 (IL-6), monocyte chemotactic protein-1 (MCP-1), plasminogen activator inhibitor-1 (PAI-1), retinol binding protein-4 (RBP4), tumor necrosis factor-a (TNF-a), and visfatin.

These factors are associated with the regulation of a wide variety of bodily processes, including blood pressure regulation, lipid metabolism, growth factors, and other complex systems, illustrating the depth of its involvement in the body’s overall metabolism. Researchers are studying these systems and pathways in order to gain a better understanding of the obese state.